Lead-free free-cutting aluminum brass alloy and its manufacturing method

The present invention provides a lead-free free-cutting aluminum brass alloy and its manufacturing method. The alloy comprises: 57.0˜63.0 wt % Cu, 0.3˜0.7 wt % Al, 0.1˜0.5 wt % Bi, 0.2˜0.4 wt % Sn, 0.1˜0.5 wt % Si, 0.01˜0.15 wt % P, at least two elements selected from the group of 0.01-0.15 wt % Mg, 0.0016-0.0020 wt % B, and 0.001-0.05 wt % rare earth elements and the balance being Zn and unavoidable impurities. The inventive alloy has excellent castability, weldability, cuttability and corrosion resistance. It is suitable for low pressure die casting, gravity casting, horizontal continuous casting, forging and extrusion. Its metal material cost is lower than bismuth brass. It is particularly applicable for components used in drinking water supply systems and other structural components. It is a new environmentally-friendly free-cutting aluminum brass alloy.